Reciprocating engine

ABSTRACT

This invention relates to a reciprocating engine which operates with a compressible working medium like steam and has a cylinder and a cooperating cylinder head. A piston moves forward and backward in the cylinder space. Steam is supplied under pressure to an outer space in the cylinder head and the flow of such steam to the cylinder space is controlled by a valve responsive to the pressure of the steam. In order to regulate the flow of steam into the cylinder space in the first part of each forward stroke of the piston, the valve is acted upon and closed by steam under pressure which becomes available to perform this function when the piston reaches a particular position in each forward stroke.

Unite States atent Hagdorn et a1.

[ 1 June 13, 1972 [54] RECIPROCATING ENGINE [72] Inventors: Manfred OttoHagdorn, Stockholm; Kjell T-Son Sandberg, Taby, both of Sweden [73]Assignee: Aktiebolaget Electrolux, Stockholm,

Sweden 22 Filed: Jan. 28, 1970 21 Appl. No.: 6,503

[30] Foreign Application Priority Data Jan. 29, 1969 Sweden... ..1174/69Dec. 16, 1969 Sweden ..17298/69 [52] US. Cl ..91/242, 91/299, 91/325[51] Int. Cl. ....E0ll 25/06, E011 21/02 [58] Field ofSearch..9l/278,224,299, 242, 325

[56] References Cited UNITED STATES PATENTS 1,804,216 5/1931 Gustafson..91/278 1,911,978 5/1933 Uhler et a1. ..91/278 2,100,541 1 1/1937Gartin ..91/278 3,361,036 1/1968 Harvey et a1 ..91/224 FOREIGN PATENTSOR APPLICATIONS 1,042,607 11/1958 Germany ..91/299 Primary Examiner-PaulE. Maslousky Attorney-Edmund A. Fenander [5 7] ABSTRACT This inventionrelates to a reciprocating engine which operates with a compressibleworking medium like steam and has a cylinder and a cooperating cylinderhead. A piston moves forward and backward in the cylinder space. Steamis supplied under pressure to an outer space in the cylinder head andthe flow of such steam to the cylinder space is controlled by a valveresponsive to the pressure of the steam. ln order to regulate the flowof steam into the cylinder space in the first part of each forwardstroke of the piston, the valve is acted upon and closed by steam underpressure which becomes available to perform this function when thepiston reaches a particular position in each forward stroke.

10 Claims, 5 Drawing Figures CONDENSER PATENTEDJUN13 m2 3, 568,974

v SHEET 1 BF 3 CONDENSER PAT NTEuJum m2 CONDENSER E Me M7 SHEET 2 OF 3PATENTEDJUN 13 1972 3. 668 974 sum 3 OF 3 CONDENSER BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates toreciprocating engines which operate with a compressible working mediumlike steam to produce power which makes it available as a rotatingtorque at a crankshaft or flywheel.

2. Description of the Prior Art For a long time reciprocating engineshave been developed for converting heat to rotating torque with steam asthe working medium. Such engines have been designed mainly for largeoutputs and information on the fundamental principles of such enginescan be obtained from general handbooks. Later, combustion engines becomeavailable which were built in small units suitable for propellingvehicles. These engines have been developed to such a degree that,because of the small space required, they now are almost the only sourceof power for automobiles.

' To an increasing degree modern military equipment requires electricpower to operate such equipment. For driving electric generators toprovide a source of electrical energy for military purposes, it isdesirable to employ portable sources of power which are silent. For thisreason, it has been proposed to employ small portable reciprocatingengines for military purposes which work with a compressible medium likesteam. Since these engines are designed primarily to drive electricgenerators they have been constructed to operate at their highestcoefficient of efficiency and output at essentially constant r.p.m.determined by the requirements of the generator.

SUMMARY OF THE INVENTION It is an objectof our invention to provide animproved reciprocating engine which operates with a compressible workingmedium like steam to produce power which makes it available as arotating torque, the speed and power of the engine being variable overwide limits. 7

We accomplish this by supplying a compressible working medium like steamto an outer space in a cylinder head and controlling the flow of suchsteam to a cylinder space by a valve responsive to the pressure of thesteam. In order to regulate the flow of steam into the cylinder space inthe first part of each forward stroke of the piston moving forward andbackward in the cylinder space, the valve is acted upon and closed bysteam under pressure which becomes available to perform this functionwhen the piston reaches a particular position in each forward stroke.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawing,

FIG. 1 is a vertical sectional view of a one-cylinder engine embodyingour invention which is normal to its crankshaft and adapted to beoperated .with a compressible gaseous medium like steam, for example;

FIG. 2 is a fragmentary sectional view of parts like those shown in FIG.1 illustrating another embodiment of the invention;

FIGS. 3 and 4 are fragmentary sectional views similar to FIG. 2illustrating other embodiments of the invention; and

FIG. 5 is a vertical sectional view of an engine like that shown in FIG.1 illustrating a further embodiment of the invention.

Engines of this type have a very limited field of use and are 2DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, thereciprocating engine embodying our invention comprises a crankshaft 10which operates in a crankcase 11 and is connected by a connecting rod 12and a piston pin 13 to a piston 15 which operates in a cylinder 14 andis provided with piston rings 17 disposed in annular grooves 16.Although not shown, the inner wall of the cylinder 14 can be providedwith a lining of suitable material, such as carbon steel, for example,having desirable heat conductive and lubricating properties. Anintermediate wall 19 is arranged between the upper end of the cylinderand a cylinder head 18 in such manner that it forms a partition betweenthe cylinder space 20 and an outer space 21 in the cylinder head 18.

The outer space 21 is connected by a conduit 22 to a source of supply ofsteam or other suitable compressible gaseous medium (not shown), so thatthe space 21 will always be at the same pressure as the steam which issupplied thereto. In FIG. 1, the moving parts of an inlet valve aredisposed above an opening 23 in the intermediate wall 19 which isconcentric with the cylinder 14 and has a diameter d.

The outer surface of the intermediate wall 19 serves as a seat for avalve body comprising a valve disc 24 which is connected by one or morerods 25 to a piston-shaped part 27,28 which is movable in an annularcavity 26 in the cylinder head 18 in a direction toward and from thevalve seat. The part 27 is cylindrical and adapted to bear and sealagainst the outer wall of the cavity 26 and the part 28, which is urgedin a direction from the valve seat by the pressure of the steam in thechamber 21, has substantially the same area as that of the opening 23which has the diameter d and with which the inlet valve coacts.

In FIG. 1 the inlet valve is shown in its closed position, that is, withthe valve disc 24 bearing against the valve seat. Since the area of thepart 28 subjected to the steam pressure in chamber 21 and having thediameter D substantially corresponds to the area of the opening 23 whichhas the diameter d, the steam in the chamber 21 exerts no openingpressure on the valve body but the valve is kept in its closed positionby a small force produced by a pressure spring 30 which is concentricwith the valve body and disposed in a space 29 in the cylinder head 18.If it should be desirable to employ the steam in chamber 21 to maintainthe valve in its closed position, this can be done'by providing a valvedisc 24 and opening 23 therefor which are correspondingly larger thanthe area of the part 28 which has the diameter D. I

The quantity of steam which flows into the cylinder space 21. duringeach stroke of the piston is determined by a conduit 33 having one endopen at 34 in the cylinder space 20 and the opposite end open at 35 inthe space 29 of the spring 30 which tends to keep the valve in itsclosed position. The space 29 is in communication with the annularcavity 26 in the cylinder head 18.

When the piston moves from its upper dead center position toward itsbottom dead center position during a working stroke, it uncovers theopening 34 of the connecting conduit 33 so that steam at essentially thepressure of the inlet steam flows through the conduit 33 into the space29 and balances the steam pressure acting on the opposite bottom side ofthe part 28 of the valve body, whereby the steam pressure acting on theparts of the valve system become balanced and the spring 30 functions toclose the valve.

While opening 34 of the connecting conduit 33 can be located at such aparticular point that the best filling of steam in the cylinder space 20will be obtained at a certain r.p.m. and with a certain load on theengine, the location of the opening 34 at such particular point will notgive an equally good result at varying loads and speeds. Therefore, theconduit 33 includes a plurality of branch conduits 37,38,39,40 which areconnected in parallel and can be connected to the conduit 33 by aselector 36. The branch conduits 37,38,39 and 40 having o enings34,4l,42,43 communicating with the cylinder space 20 which are locatedat different distances from the dead center position of the piston 15.The selector 36 comprises a casing 44 within which is disposed arotatable ring 46 having an opening 47 which can be selectively placedin communication with any one of the branch conduits 37,38,39,40.

The engine illustrated in FIG. 1 operates like a direct current engine,that is, the working medium is admitted into the s ace 20 when thepiston is in its top dead center position and is discharged therefromwhen the piston is close to its bottom dead center position. The outletfor the working medium is formed by one of several ports in the wall ofthe cylinder 14. I During the working stroke, the working medium expandsduring movement of the piston 15 from its top dead center positiontoward its bottom dead center position. When the top piston ring 17 ofthe piston 15 passes the edge 49 of a port 48, the more or less expandedworking medium commences to flow from the space through the port. Suchoutward fiow of the working medium continues while the piston movesdownward and then moves upward until the piston ring 17 passes the edge49 of the port during upward movement of the piston 15 to its top centerposition.

While the piston 15 is moving downward during its working stroke withthe inlet valve closed, the pressure of the steam decreases in thecylinder space 20 and also in the conduit 33 and for this reason, duringthis entire period, the steam pressure in the cylinder space 20 at thebottom of the valve disc 24 balances the pressure transmitted from theconnecting conduit 33 to the outside of the piston-shaped part 27,28 ofthe valve.

While the piston 15 is moving toward its top dead center position a lossby compression would occur if an outlet valve 50 like that shown in FIG.1 were not provided. The outlet valve 50 is connected to an opening 51in the wall of the cylinder 14, such opening having its upper edge 52located at a somewhat greater distance from the intermediate wall 19than the distance therefrom to the top piston ring 17 when the piston 15is in its top dead center position.

The outlet valve 50 comprises a valve disc 53 which, during the workingstroke, is moved against a valve seat 54 by the pressure of the steam inthe space 20 against the action of a pressure spring 55 which isadjusted so that it will be capable of moving the valve disc 53 from itsseat 54 against the action of the exhaust pressure in the space 20during the exhaust stroke of the piston 15. In this way losses resultingfrom compression work in the engine that is not utilized are prevented.

The position of the opening 51 in the cylinder wall can be selected sothat the valve, after the piston 15 has passed the opening, causes acertain compression of the body of steam enclosed in the space 20 sothat a pressure on the inlet valve is produced which lifts the valvedisc 24 a small amount. When this occurs, inlet steam flows from thespace 21 into the cylinder space 20 and the pressures on the top andbottom sides of the valve disc 24 are equalized and the pressure of theinlet steam in the space 21 on the part 28 of the valve body will liftthe valve disc 24 completely from its seat and steam will flow into thecylinder space 20 and cause the piston 15 to move downward toward itsbottom dead center position while the steam is expanding.

The reciprocating steam engine just described and shown in FIG. 1 ischaracterized by the absence of any venting provisions to the atmospherewhich is costly. This is so because the valve body, which includes thepistonshaped parts 27 and 28, would not be balanced on steam underpressure if the valve body were vented to atmosphere. As seen in FIG. 1,therefore, the outer space 21 is sealed from the atmosphere, and, aspointed out above, this space will always be at the same pressure as thesteam which is supplied thereto.

Further, by providing the connecting conduit or passageway means 33exteriorly of the cylinder wall 14 and only extending the horizontalpassageway means 37 to 40 through the cylinder wall the volume of thedead spaces in communication with the cylinder space 20 is at a minimum.The manually operable selector 36 interposed between the verticalconduit 33 and horizontal passageway means 37 to 40 provides anarrangement which enables the reciprocating engine to be driven atvarious speeds which can easily be controlled manually by the handle ofthe selector or control 36.

The steam inlet arrangement shown in FIG. 1 and just described can bevaried in many ways within the scope of our invention. FIG. 2illustrates a modification in which a plurality of openings 60 areprovided between the outer space 121 and the cylinder space 120. Partsin FIG. 2 which are similar to parts in FIG. 1 are designated by thesame reference numerals to which is added. Over the intermediate wall119 is positioned a valve disc 124 which is in the form of a clover leafhaving the same number of leaves as the number of openings 60. Betweenadjacent leaves is provided a pin 61 that prevents rotating movement ofthe valve disc 124. The part 128 of the valve body is of conical shapeand is guided in a space 129 in which the spring is disposed. Anadjusting screw 62 coacts with the spring 130 to adjust the force of thespring.

The selector 136 is provided with an inner sleeve 146 turnable by an arm63. The sleeve 146 is provided with a plurality of openings 147 whichare so positioned that, by turning the arm 63, the conduit 133 can beconnected to any one of the branch conduits having openings 141,142 and143 in communication with the cylinder space 120. The valve body 124,128consists of separate parts which are connected by a sleeve 64 threadedon a tap 65 fixed to the part 128. The sleeve 64 has an inner shoulder66 for the spring 132 and an outer shoulder 67 against which the valvedisc 124 and a cylindrical part 68 rest. The inlet valve arrangementshown in FIG. 2 operates in the same way as the corresponding inletvalve arrangement shown in FIG. 1 and just described.

As in the first-described embodiment the outer space 121 in FIG. 2 issealed from the atmosphere. Further, the volume of the dead spaces incommunication with the cylinder space 121 is still at a minimum for thereason that only a single vertical passageway 133 extends downward fromthe cylinder head 1 18 to the manually operable control or selector 136.

Another modification of an inlet .valve arrangement is shown in FIG. 3in which certain parts are similar to parts in FIG. 1 and other partsare similar to parts in FIG. 2. In FIG. 3 the valve disc 224 is like thevalve disc 124 in FIG. 2 and the remainder of the valve body is disposedin a space 226 about a central space 229 in which the spring 230 islocated. The pressure of the inlet steam in the space 221 acts upon asurface 70 having an area corresponding to the area of the openings 260.The valve body 71 also has a wider part 72, the inner or upper side ofwhich is subjected to the pressure in the connecting conduit 233, sothat a greater closing force acting on the valve can be obtained. One ofthe cylindrical parts 71' and 72 of the valve body 71 or both of theseparts can slide sealingly against an outer sealing ring 70' during themovement of the valve body.

A further modification of the inlet valve arrangement is shown in FIG.4. In FIG. 4 a valve disc 80 of steel is fixed to a central tap 81 whichin turn is connected to a diaphragm 82, the peripheral edge portion ofwhich is fixed in the cylinder head 318. The spring 330 bears against acentral portion of the diaphragm 82 which can be made of suitableresilient material or of metal and also can be formed like a bellows. Anadjustable throttle device comprising a screw 83 is provided in theconduit connection 333. This is suitable in the case of a reciprocatingengine that operates with a constant filling of steam or other workingmedium.

When a stationary one-cylinder engine having an inlet valve arrangementembodying our invention is started, the crankshaft 10 is rotated so thatthe piston moves upward to a position suitable for starting. When thepiston is in such starting position the inlet valve is opened bysuitable mechanism which can be operated electrically, mechanically orpneumatically, for example. By way of example, an electromagnet (notshown) can be employed to open the inlet valve. In the embodiment shownin FIG. 1, a spring 32 is provided at the bottom of the valve'disc 24 sothat the top surface 31 of the piston 15, during upward movement of thepiston toward its top dead center position, will act on the spring 32and lift the valve disc a small amount. After this occurs the pressureof the inlet steam will cause the valve to open completely.

In the modification of FIG. 3 is shown an arrangement for starting theengine pneumatically. A space 73 exteriorly of the valve piston 71 isconnected by a conduit 74 to a condenser which prevents a pressurebuild-up in the space 73 during operation of the engine. However, duringstarting of the engine the pressure medium can be admitted in the space73 to effect lifting of the valve disc 224. It is also possible to startthe engine with a negative pressure from the condenser at the oppositeside of the piston.

When a starting device is actuated by a suitable impulse, it isdesirable either to control the position of the piston in order thatstarting will be initiated with the piston in a proper stating position,or to employ an automatic device which prevents starting of the enginewhen the piston is not in a proper starting position. In a one-cylinderengine like that shown and described, a flywheel provided with asuitable marking can be turned to a proper starting position. Absence ofcompression in the engine will not prevent such movement of theflywheel.

In a multiple-cylinder engine there will always be some piston in aproper starting position for starting the engine. Under these conditionsthe starting device desirably should be combined with a sensinginstrument to indicate which one of the engine cylinders must besupplied with steam to start the engine. An arrangement of this kind canbe provided which will function automatically to start the engine.

A starting device of the kind referred to in connection with FIG. 3 isdiagrammatically shown in detail in FIG. 5. In FIG. 5 a piston 411having piston rings 412 is adapted to reciprocate in a cylinder 410.Outside the cylinder an outer space 413 is provided to which acompressible medium like steam, for example, is supplied through aconduit 414. An intermediate wall 415 between the cylinder 410 and theouter space 413 has an opening 416 adapted to be closed by a valve disc417 forming part of an inlet valve. The valve disc 417 is connected by abolt 418 to a valve body 419 which is vertically movable and includes afirst cylindrical part 420 sealingly arranged against an outer ring 421and a second wider cylindrical part 422 sealingly arranged against acorresponding surface of the ring 421. Thediameter of the cylindricalpart 420 is desirably such that the steam pressure in the outer space413 on the valve disc 417 in a downward direction toward the valve seatand the steam pressure in the upward opposite direction on the valvebody 419 are balanced. The valve disc 417 is biased toward its valveseat by a'centrally disposed spring 423 arranged in a chamber 424.

When the engine shown in FIG. 5 is being operated the inlet valve417,419 opens due to the steam compression produced in the cylinderspace 410 during the latter part of the upward movement of the piston411. When the valve 417, 419 has opened a small amount the balancing ofthe steam pressures on the valve body 419 ceases and the valve will moveto its wide open position and steam will flow into the cylinder space410. Downward movement is imparted to the piston 411. Thereafter theconduit connection established between the cylinder space 410 and thespring chamber 424 will cause the inlet valve 417,419 to close at aparticular time.

The conduit connection just referred to includes a passageway 425between the spring chamber 424 and a space 426 in which a sleeve 428 isrotatable by a handle 427. The sleeve 428 is provided with a pluralityof openings 429 which are provided along a helical line and the cylinderwall 430 is formed with a series of channels 431, 432, 433, 434, 435which are located at different distances from the intermediate wall 415.

The degree of filling of the cylinder, that is, the quantity of steamadmitted into the cylinder space 410 for each working stroke of thepiston 411, can be determined by adjusting the rotatable sleeve 428 bythe handle 427. In FIG. 5 the sleeve 428 is in such a position that oneof the openings 429 communicates with the channel 433 in the cylinderwall 430. Under these conditions steam will flow into the cylinder space410 during downward movement of the piston 411 until the top piston ring412 has passed the channel 433.

When this occurs steam from the cylinder space 410 will flow through thechannel 433, an opening 429, space 426 and passageway 425 to the springchamber 424. In chamber 424 the valve body 419 will be subjected to thissteam pressure and impart downward movement to the valve 417,419 419 andclose the opening 416. The valve diaphragm 417 moved downward on itsseat very quickly and cuts off the admission of steam into the space ina manner which, to a great extent, is independent of the r.p.m. of theengine. The steam present in the cylinder 410 expands during thedownward movement of the piston 411 until the top piston ring 412 haspassed the edges 436 of a plurality of outlet openings 437 leading to anannular space 438 having an outlet 448' in communication with acondenser.

An outlet valve 450, which is like the outlet valve 50 in FIG. 1 anddescribed above and serves the same purpose, is connected to an opening451 in the wall of the cylinder 430. The outlet valve 450 comprises avalve disc 453 which, during the working stroke, is moved against avalve seat 454 by the pressure of the steam in the space 410 against theaction of a pressure spring 455 which is adjusted so that it will becapable of moving the valve disc 453 from its seat 454 against theaction of the exhaust pressure in the space 20 during the exhaust strokeof the piston 411.

Exteriorly of the valve body 419 in the cylinder head 439 and betweenthe valve body and the sealing ring 421 is provided a space, 440 towhich is connected one end of a passageway 441,444, the other end ofwhich is connected to the annular passageway 438. If desired, the lowerend of the passageway 441,444 can be connected directly to the condenserin communication with the annular passage 438. In this way the valvebody 419 is prevented from being subjected to any pressure tending toimpede its movement.

In accordance with our invention the space 440 is employed to start thereciprocating engine. As shown, a passageway 442 is provided in thecylinder head 439 which extends between the passageway 441 and the outerspace 413 in which the inlet steam pressureprevails. A push rod 443having a sealing ring 449 is axially movable in the passageway 442. Whenthe push rod 443 is moved inward, the sealing ring 449 closes thepassageway 441 so that passageway 444 which is associated therewith, nolonger will be connected-to the annular passage 438. The push rod 443 isprovided with a valve device or disc 446 disposed in an inner enlargedportion 445 of the passageway 442. When the push rod 442 is moved inwardvalve device or disc 446 moves from its seat a small amount to establishcommunication between the inlet steam space 413 and the space 440. Whenthis occurs the steam under pressure functions to move the valve deviceor disc 446 to its wide open position. In order to maintain the sealingring 449 and valve device or disc 446 in the positions illustrated inFIG. 5 with the connection 441,444 to the annular passage 438 orcondenser open and the connection from the outer steam inlet space 413to the space 440 closed, a spring 447 is disposed between the cylinderhead 439 and a pair of lock nuts 448 on the push rod Steam underpressure flows from the inlet steam space 413 to the space 440 only whenthe piston 411 is in a proper position whereby the steam admitted underpressure into the cylinder space 410 will be capable of moving thepiston in the intended direction. In accordance with our inventionstructure can be provided which is dependent upon the positions of thepiston 411 and the crankshaft and operatively associated with the valvedevice or disc 446 so that the valve device cannot be opened by thepressure of steam in the steam inlet space 413 until the piston is in aproper position for starting the engine.

In a multiple-cylinder engine, there is always one piston in a properposition for starting the engine. In accordance with our invention,therefore, the engine can be equipped with a lowpressure connection fromthe steam inlet space 413 to the space 440 and with a connection fromthe steam inlet space 413 to each cylinder and the starting device canbe provided with structure which is dependent on the position of thecrankshaft whereby, when the engine is started, steam from the inletsteam space 413 will automatically flow into the space 440 near thatpiston which is in the most proper starting position.

The reciprocating engine just described has many interestingcharacteristics. Due to its simple construction the engine hasrelatively small dimensions for a given output. By reason of itssimplicity it is easy to handle and is safe in operation and itsoperating qualities make it usable for most purposes requiring a sourceof power. It can be so balanced that it operates with only slightvibrations. The engine can readily be manufactured with a plurality ofcylinders whereby the torque on the crankshaft will be more even than ina one-cylinder engine.

When a combustion engine of an automobile is replaced by an engine ofthe kind herein described, the qualities of the engine embodying ourinvention not only produce the source of power itself but to a greatextent also provide the torque converter to be replaced because theoutput at different r.p.m. of the engine described above is quitedifferent from that of combustion engines. Furthermore, the torque ofthe engine can be used within a much wider range than in the case of acombustion engine. All these features contribute to the assumption thatthe costs of a power plant based on the new engine will be considerablylower than those of a corresponding combustion engine with gearmechanisms or torque converters.

It will be understood that the steam exhausted from the engine can bedischarged into the ambient air. When this cannot be done conveniently,a closed circulation path for the working medium can be employed whichincludes a condenser from which liquid working medium returns to thesteam generator. At the same time a heat exchanger can be provided inwhich steam exhausted from the engine flows in heat exchange relationwith water supplied to the steam generator.

We claim:

1. In combination,

a. a reciprocating engine having a cylinder and a cylinder headtherefor, said cylinder defining a working space,

a piston for said cylinder which is movable forward and backward thereinin a path of movement,

. said cylinder head defining an outer space which is outside theworking space of said cylinder and adapted to receive a compressibleworking medium under pressure,

d. an apertured wall between the outer space and the working space, saidwall having an opening,

. valve means movable to and from a closed position at the opening,

said valve means including a valve body,

. means for controlling said valve body responsive to the pressure ofthe working medium,

. means for regulating the influence of the working medium on themovement of said valve body responsive to the position of said piston inits path of movement in said cylinder,

. spring means for biasing said valve body toward the opening in saidapertured wall to move said valve means to its closed position,

I said cylinder head having a space in which said spring means isdisposed,

k. means providing a passageway between the working space of saidcylinder and said spring means space, said passageway at one end havingan opening at the inside wall of said cylinder,

. the pressure of the working medium in said spring means space on saidvalve body balancing the pressure in the outer space on said valve bodyin a direction opposite to the biasing action of said spring meanswhereby said spring means becomes effective to move said valve means toits closed position responsive to movement of said piston from saidcylinder head past the opening of said passageway at the inside wall ofsaid cylinder to a position at which the last-mentioned opening is incommunication with the working space of said cylinder,

m. means providing a first chamber exteriorly of said valve body whichis defined in part by the latter,

n. means providing one passageway between said outer space and saidfirst chamber,

0. first valve structure for controlling flow of working medium in saidone passageway from said outer space to said first chamber, and

p. the part of said valve body defining said first chamber having asurface for imparting movement to said valve means in a direction fromsaid apertured wall when said first valve structure is open and workingmedium flows from said outer space to said first chamber.

2. A reciprocating engine as set forth in claim 1 which includes meansproviding a second low-pressure chamber, such as a condenser, forexample, means providing another passageway between said first andsecond chambers, and second valve structure in said other passagewaybetween said first and second chambers, said second valve structurebeing closed when said first valve structure is open.

3. A reciprocating engine as set forth in claim 2 in which said enginehas a single cylinder, and means for opening said first valve structureto start said engine when said piston is in a proper position to effectsuch starting.

4. A reciprocating engine as set forth in claim 3 which includes meanscoupling said first and second valve structures in such manner that saidfirst valve structure is closed when said second valve structure is openand vice versa, and spring means biasing said coupling means to urgesaid first valve structure to its closed position and said second valvestructure to its open position.

5. A reciprocating engine as set forth in claim 1 in which said enginehas a single cylinder, and means for opening said first valve structureto start said engine when said piston is in a proper position to effectsuch starting, said means being dependent on the position of the pistonand hence of the crankshaft so that the valve for inlet pressure cannotbe opened until the piston is in a position suitable for starting theengine.

6. A reciprocating engine as set forth in claim 1 in which said enginehas at least two cylinders and means to start said engine by openingsaid first valve structure in the passageway to said first chamber inthe cylinder head of the cylinder in which the piston is in the bestposition for start.

7. In combination,

a. a reciprocating steam engine having a cylinder and a cylinder headtherefor, said cylinder defining a working space,

b. a piston for said cylinder which is movable forward and backwardtherein in a path of movement,

c. said cylinder head defining an outer space which is outside theworking space of said cylinder and sealed from the atmosphere andadapted to receive steam under pressure,

d. an apertured wall between the outer space and the working space, saidwall having an opening,

e. valve means movable to and from a closed position at the opening,

f. said valve means including a valve body,

g. means for controlling said valve body responsive to the pressure ofthe steam,

h. means for regulating the influence of the steam on the movement ofsaid valve body responsive to the position of said piston in its path ofmovement in said cylinder,

i. spring means for biasing said valve body toward the opening in saidapertured wall to move said valve means to its closed position,

j. said cylinder head having a space in which said spring means isdisposed,

k. means providing a passageway between the working space of saidcylinder and said spring means space, said passageway at one end havingan opening at the inside wall of said cylinder, and

l. the pressure of the steam in said spring means space on said valvebody balancing the pressure in the outer space on said valve body in adirection opposite to the biasing action of said spring means wherebysaid spring means becomes effective to move said valve means to itsclosed position responsive to movement of said piston from said cylinderhead past the opening of said passageway at the inside wall of saidcylinder to a position at which the lastmentioned opening is incommunication with the working space of said cylinder.

8. The combination set forth in claim 7 in which said valve body has afirst surface in said spring means space which, when acted upon by thesteam in the last-mentioned space, tends to move said valve means in afirst direction toward the opening in said apertured wall, said valvebody having a second surface which, when acted upon by the steam in saidouter space, tends to move said valve means in a second oppositedirection from the opening in said apertured wall, the first surfacehaving an area greater than the second surface so that the biasingaction of said spring means and the product of the pressure of the steamand the difference in area between the first and second surfaces becomeseffective to move said valve body toward the opening in said aperturedwall and move said valve means to its closed position.

9. The combination set forth in claim 7 in which said means providingsaid passageway between the working space of said cylinder and saidspring means space includes a first portion having a first opening atthe inside wall of said cylinder and at least one additional portion inparallel with said first portion also having an opening 'at the insidewall of said cylinder, said openings at the inside wall of said cylinderbeing at different distances from said apertured wall having theopening, and selecting means for rendering any one of said portionsactive and the remainder inactive to control the speed of the engine.

10. A reciprocating steam engine as set forth in claim 7 in which saidcylinder has a clearance volume of such size that, when said piston ismoving toward said apertured wall during its backward movement, thecompression developed therein will be capable of moving said valve meansfrom its closed position against the biasing action of said spring meansto equalize the pressure of the steam in said cylinder and in said outerspace, whereupon the steam acting on said valve body functions to movesaid valve means to its wide open position and keep it in such positionagainst the biasing action of said spring means.

1. In combination, a. a reciprocating engine having a cylinder and acylinder head therefor, said cylinder defining a working space, b. apiston for said cylinder which is movable forward and backward thereinin a path of movement, c. said cylinder head defining an outer spacewhich is outside the working space of said cylinder and adapted toreceive a compressible working medium under pressure, d. an aperturedwall between the outer space and the working space, said wall having anopening, e. valve means movable to and from a closed position at theopening, f. said valve means including a valve body, g. means forcontrolling said valve body responsive to the pressure of the workingmedium, h. means for regulating the influence of the working medium onthe movement of said valve body responsive to the position of saidpiston in its path of movement in said cylinder, i. spring means forbiasing said valve body toward the opening in said apertured wall tomove said valve means to its closed position, j. said cylinder headhaving a space in which said spring means is disposed, k. meansproviding a passageway between the working space of said cylinder andsaid spring means space, said passageway at one end having an opening atthe inside wall of said cylinder, l. the pressure of the working mediumin said spring means space on said valve body balancing the pressure inthe outer space on said valve body in a direction opposite to thebiasing action of said spring means whereby said spring means becomeseffective to move said valve means to its closed position responsive tomovement of said piston from said cylinder head past the opening of saidpassageway at the inside wall of said cylinder to a position at whichthe last-mentioned opening is in communication with the working space ofsaid cylinder, m. means providing a first chamber exteriorly of saidvalve body which is defined in part by the latter, n. means providingone passageway between said outer space and said first chamber, o. firstvalve structure for controlling flow of working medium in said onepassageway from said outer space to said first chamber, and p. the partof said valve body defining said first chamber having a surface forimparting movement to said valve means in a direction from saidapertured wall when said first valve structure is open and workingmedium flows from said outer space to said first chamber.
 2. Areciprocating engine as set forth in claim 1 which includes meansproviding a second low-pressure chamber, such as a condenser, forexample, means providing another passageway between said first andsecond chambers, and second valve structure in said other passagewaybetween said first and second chambers, said second valve structurebeing closed when said first valve structure is open.
 3. A reciprocatingengine as set forth in claim 2 in which said engine has a singlecylinder, and means for opening said first valve structure to start saidengine when said piston is in a proper position to effect such starting.4. A reciprocating engine as set forth in claim 3 which includes meanscoupling said first and second valve structures in such manner that saidfirst valve structure is closed when said second valve structure is openand vice versa, and spring means biasing said coupling means to urgesaid first valve structure to its closed position and said second valvestructure tO its open position.
 5. A reciprocating engine as set forthin claim 1 in which said engine has a single cylinder, and means foropening said first valve structure to start said engine when said pistonis in a proper position to effect such starting, said means beingdependent on the position of the piston and hence of the crankshaft sothat the valve for inlet pressure cannot be opened until the piston isin a position suitable for starting the engine.
 6. A reciprocatingengine as set forth in claim 1 in which said engine has at least twocylinders and means to start said engine by opening said first valvestructure in the passageway to said first chamber in the cylinder headof the cylinder in which the piston is in the best position for start.7. In combination, a. a reciprocating steam engine having a cylinder anda cylinder head therefor, said cylinder defining a working space, b. apiston for said cylinder which is movable forward and backward thereinin a path of movement, c. said cylinder head defining an outer spacewhich is outside the working space of said cylinder and sealed from theatmosphere and adapted to receive steam under pressure, d. an aperturedwall between the outer space and the working space, said wall having anopening, e. valve means movable to and from a closed position at theopening, f. said valve means including a valve body, g. means forcontrolling said valve body responsive to the pressure of the steam, h.means for regulating the influence of the steam on the movement of saidvalve body responsive to the position of said piston in its path ofmovement in said cylinder, i. spring means for biasing said valve bodytoward the opening in said apertured wall to move said valve means toits closed position, j. said cylinder head having a space in which saidspring means is disposed, k. means providing a passageway between theworking space of said cylinder and said spring means space, saidpassageway at one end having an opening at the inside wall of saidcylinder, and l. the pressure of the steam in said spring means space onsaid valve body balancing the pressure in the outer space on said valvebody in a direction opposite to the biasing action of said spring meanswhereby said spring means becomes effective to move said valve means toits closed position responsive to movement of said piston from saidcylinder head past the opening of said passageway at the inside wall ofsaid cylinder to a position at which the last-mentioned opening is incommunication with the working space of said cylinder.
 8. Thecombination set forth in claim 7 in which said valve body has a firstsurface in said spring means space which, when acted upon by the steamin the last-mentioned space, tends to move said valve means in a firstdirection toward the opening in said apertured wall, said valve bodyhaving a second surface which, when acted upon by the steam in saidouter space, tends to move said valve means in a second oppositedirection from the opening in said apertured wall, the first surfacehaving an area greater than the second surface so that the biasingaction of said spring means and the product of the pressure of the steamand the difference in area between the first and second surfaces becomeseffective to move said valve body toward the opening in said aperturedwall and move said valve means to its closed position.
 9. Thecombination set forth in claim 7 in which said means providing saidpassageway between the working space of said cylinder and said springmeans space includes a first portion having a first opening at theinside wall of said cylinder and at least one additional portion inparallel with said first portion also having an opening at the insidewall of said cylinder, said openings at the inside wall of said cylinderbeing at different distances from said apertured wall having theopening, and selecting means for rendering any one of said portionsactive and thE remainder inactive to control the speed of the engine.10. A reciprocating steam engine as set forth in claim 7 in which saidcylinder has a clearance volume of such size that, when said piston ismoving toward said apertured wall during its backward movement, thecompression developed therein will be capable of moving said valve meansfrom its closed position against the biasing action of said spring meansto equalize the pressure of the steam in said cylinder and in said outerspace, whereupon the steam acting on said valve body functions to movesaid valve means to its wide open position and keep it in such positionagainst the biasing action of said spring means.